Function primary_cost 

pub fn primary_cost<S>(
    spell: &SpellDataFlat,
    primary_resource_type: i32,
    modifiers: &PowerModifiers,
    active_aura_spell_ids: &HashSet<i32, S>,
) -> (f64, i32)
where
    S: BuildHasher,

Primary power cost (descaled) and its power type, matched by resource type; -1 when absent.